Dual mechanisms of peroxymonosulfate activation by a CoCuLDH/CoCuMOF composite for pollutant degradation via radical and nonradical pathways

Abstract Peroxymonosulfate (PMS)-based advanced oxidation processes have attracted considerable attention for degrading persistent organic pollutants in wastewater. However, developing efficient and stable catalysts for PMS activation remains a challenge. This study aims to design hybrid catalysts combining layered double hydroxide (LDH) and metal-organic framework (MOF) structures to enhance catalytic performance through interfacial synergy. Two bimetallic composites, CoCu-LDH@CoCu-MOF (LM) and CoCu-MOF@CoCu-LDH (ML), were synthesized and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, scanning electron microscopy, and transmission electron microscopy. Their catalytic performance was evaluated in PMS-activated degradation of organic pollutants under optimized conditions, supported by radical quenching and reusability tests. LM showed superior catalytic activity, achieving 98.9% degradation of methylene blue (MB) within 10 min., and effectively degrading other pollutants Under the same optimized conditions, the LM/PMS system also achieved 99.6% removal of crystal violet (CV) and complete (100%) removal of malachite green (MG) within 10 min, along with 91.1% removal of p-nitrophenol (PNP) and 82.7% removal of tetracycline hydrochloride (TCH) within the same time frame, confirming the broad applicability of the system toward structurally diverse organic contaminants. Mechanistic studies indicated that singlet oxygen ( 1 O 2 ) was the dominant reactive species, with additional contributions from hydroxyl, sulfate, and superoxide radicals. The catalyst retained 96.9% removal efficiency after three cycles. This performance is attributed to the synergistic LDH-MOF interface, which enhances reactive species generation and provides abundant active sites for efficient PMS activation.